/*  Shared Memory Lock Routines
 *
 *  This shared memory locked queue support routine need to be
 *  able to lock the specified locked queue.  Interrupts are
 *  disabled while the queue is locked to prevent preemption
 *  and deadlock when two tasks poll for the same lock.
 *  previous level.
 *
 *  COPYRIGHT (c) 1989-1999.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  lock.c,v 1.9.4.1 2003/09/04 18:44:56 joel Exp
 */

#include <rtems.h>
#include <bsp.h>
#include <shm_driver.h>


/*
 *  Shm_Initialize_lock
 *
 *  Initialize the lock for the specified locked queue.
 */

void Shm_Initialize_lock(
  Shm_Locked_queue_Control *lq_cb
)
{
  lq_cb->lock = LQ_UNLOCKED;
}

/*  void _Shm_Lock( &lq_cb )
 *
 *  This shared memory locked queue support routine locks the
 *  specified locked queue.  It disables interrupts to prevent
 *  a deadlock condition.
 */

asm(
    ".text\n"
    ".align 4\n"
"LEON3_Atomic_Swap:\n"
"	retl\n"	
"	swapa [%o1] 1, %o0\n"
); 
									


void Shm_Lock(
  Shm_Locked_queue_Control *lq_cb
)
{
  uint32_t isr_level;
  uint32_t *lockptr = (uint32_t *) &lq_cb->lock;
  uint32_t lock_value;

  lock_value = SHM_LOCK_VALUE;
  rtems_interrupt_disable( isr_level );

    Shm_isrstat = isr_level;
    while ( lock_value ) {
      lock_value = LEON3_Atomic_Swap(lock_value, lockptr);
/*       asm volatile( "" */
/*                          : "=r" (lockptr), "=r" (lock_value) */
/*                          : "0" (lockptr),  "1" (lock_value) */
/*                   ); */
      /*
       *  If not available, then may want to delay to reduce load on lock.
       */

/*       if ( lock_value ) */
/*         rtems_bsp_delay( 10 );   /\* approximately 10 microseconds *\/ */
   }
}

/*
 *  Shm_Unlock
 *
 *  Unlock the lock for the specified locked queue.
 */

void Shm_Unlock(
  Shm_Locked_queue_Control *lq_cb
)
{
  uint32_t isr_level;

  lq_cb->lock = SHM_UNLOCK_VALUE;
  isr_level = Shm_isrstat;
  rtems_interrupt_enable( isr_level );
}

